Unsteady free-surface wave-induced separation: analysis of turbulent structures using detached eddy simulation and single-phase level set

Turbulent structures of the unsteady free-surface wave-induced separation around a surface-piercing NACA0024 are studied using a detached-eddy simulation with a single-phase level set method. Quantitative verification and validation show good agreement with experimental data. Instantaneous and mean flows show an owl-type separation with the same instability frequencies identified by unsteady Reynolds-averaged Navier–Stokes. Anisotropy invariant maps show that turbulence is anisotropic in the middle of the separation region and is at a two-component state near the foil surface. The turbulent kinetic energy and its budget have similarities to that of a separated turbulent boundary layer near the toe and a backward-facing step flow in the recirculation region, but with large three-dimensional and free-surface effects. The free-surface damps velocity and pressure fluctuations and moves the peaks of turbulence quantities from the high-speed to the low-speed side of the free shear layer.

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